Experiment No: 02

Sieve Analysis of Fine Aggregate

Introduction

Aggregates, an essential component in construction, are materials like sand, gravel, or crushed stone that are added to cement and water to form concrete. They may be divided into two types: fine and coarse.

Sieve Analysis is a crucial test method in civil engineering, especially for analyzing aggregates. The process entails grading aggregates, both fine and coarse, by sieving to determine their size distribution.

Sieve analysis is a well-established method in the study of materials used to determine the particle size distribution of granular material. This approach is frequently employed across several sectors, with a particular emphasis in construction and civil engineering for analyzing fine and coarse aggregates.

Fineness modulus is only a numerical indicator of fineness giving some sense of the mean size of particles in the entire body of aggregate. Determination of fineness modulus may be viewed as a way of standardizing of the grading of the aggregates. It is achieved by sieving a known mass of specified aggregate on a set of standard sieves and by adding the cumulative percentages of mass of material retained on all the sieves and dividing the total percentage by 100.

Scope

This test method involves the determination of the particle size distribution of fine aggregates by sieving.

Purpose

·        To determine the particle size distribution of fine aggregate by sieving

ASTM Designation

·        ASTM C136/C136M-19

·         ASTM C33/C33M-08

Terminology

Aggregate

Granular material, such as sand, gravel, crushed stone, or iron blast-furnace slag, mixed with a cementing medium to make hydraulic-cement concrete or mortar.

Coarse aggregate –

(1)  aggregate mostly retained on the 4.75-mm (No. 4) sieve; or

(2)  that fraction of an aggregate remained on the 4.75-mm (No. 4) sieve

Fine aggregate –

(1)  aggregate passing the 9.5-mm (3⁄8-in.) sieve and basically completely passing the 4.75-mm (No. 4) sieve and mostly retained on the 75-µm (No. 200) sieve; or

(2)  that fraction of an aggregate passing the 4.75-mm (No. 4) sieve and retained on the 75-µm (No. 200) sieve.

Fineness Modulus of aggregate

·        a factor obtained by adding the percentages of material in the sample that is coarser than each of the following sieves (cumulative percentages retained), and dividing the sum by 100.

Significance

This test method is used mainly to determine the grading of materials intended for use as aggregates or being utilized as aggregates. The findings are used to assess compliance of the particle size distribution with applicable specification criteria and to provide essential data for control of the manufacture of various aggregate products and mixtures incorporating aggregates. The data may also be useful in generating correlations relating porosity and packing.

Apparatus

·        Balances or scales with a minimum accuracy of 0.1 g for fine Aggregate

·        Standard Sieves conforming to the requirements of Specification E11

·     Mechanical sieve shaker: The sieving action shall be such that the criterion for adequacy of sieving is met in a    reasonable time period.

·        Oven capable of maintaining a uniform temperature of 110 ± 5°C [230 ± 10°F]

Sampling

Fine Aggregate—The size of the test sample, after drying, shall be 300 g minimum.

Procedure

[1]  Dry the sample to constant mass at a temperature of 110 ± 5 °C [230 ± 10 °F]

[2] Select sieves with appropriate apertures to provide the necessary information as stated in the specifications for the item being tested. Use further sieves as needed to obtain additional data, including fineness modulus, or to control the quantity of material on a sieve. Arrange the sieves in descending order of opening size, with the largest opening at the top, then place the sample on the top sieve. The pan is placed at the bottom­most position. Stir the sieves manually or with a mechanical device for a certain duration determined through trial or verified by measuring the actual test sample to ensure it meets the required standard.

2.1 The manual method should be performed in a proper sequence which is as follows:

                                                                            I.            ­forward and backward motion

                                                                         II.            left and right motion

                                                                      III.            clockwise (CW) and counter­clockwise (CCW) motion

                                                                     IV.            frequent jolting.

2.2 For mechanical device:

Sieve the material for an adequate amount of time such that, after finishing, no more than 1% by weight of the material retained on any one sieve will pass through that sieve in 1 minute of continuous hand sieving as described. Hold the individual sieve, equipped with a tight-fitting pan and cover, at a slightly tilted angle with one hand.
Strike the side of the sieve hard and with an upward motion against the heel of the other hand at a frequency of approximately 150 times per minute, rotating the sieve roughly one sixth of a rotation every 25 strokes.

[3] Limit the amount of material on a sieve to ensure that all particles have many opportunities to pass through the sieve apertures throughout the sieving process. The amount of material left on a sieve with apertures smaller than 4.75-mm should not be more than 7 kg/m2 of the sieving surface area. The amount of material retained in kilograms on sieves with apertures of 4.75 mm (No. 4) or greater should not exceed 2.5 times the product of the sieve opening in millimeters and the effective sieving area in square meters. In no situation may the quantity retained be so large as to cause forever distortion of the sieve cloth

[4] Prevent an overload of material on an individual sieve by one of the following methods:

4.1  Insert an extra sieve with opening size intermediate between the sieve that may be overloaded and the sieve immediately above that sieve in the original set of sieves.

4.2  Split the sample into two or more pieces, sieving each component independently. Combine the masses of the several portions maintained on a given sieve before computing the percentage of the sample on the sieve.

4.3  Use sieves with a bigger frame size and providing greater sieving area.

[5]  Determine the mass of each size increment on a scale or balance conforming to the requirements to the nearest 0.1 % of the total original dry sample mass. Compare the total mass of the material after sieving to the initial dry sample mass placed on the sieves. If the quantities vary by more than 0.3 %, based on the original dry sample mass, do not use the data for acceptance purposes.

Calculation

·        Calculate percentages passing, total percentages retained, or percentages in various size fractions to the nearest 0.1 % on the basis of the total mass of the initial dry sample.

·        Calculate the fineness modulus

·        Plot the grain size distribution on a semi log graph paper

Report

I.            Depending upon the form of the specifications for use of the material under test, the report shall include the following:

·      Total percentage of material passing each sieve, or

·      Total percentage of material retained on each sieve,

·      Percentage of material retained between consecutive sieves.

II.            Report percentages to the nearest whole number, except if the percentage passing the 75-µm (No. 200) sieve is less than 10 %, it shall be reported to the nearest 0.1 %.

III.            Report the fineness modulus, when required, to the nearest 0.01

Grading Requirement

Grading simply demonstrates the sizes of the aggregates and in which quantities they are present. There are some limitation parameters for every sieve specified by ASTM.

ASTM Grading Requirements for Fine Aggregates

Sieve (Specification E11)	Percent Passing
9.5-mm (3⁄8-in.)	100
4.75-mm (No. 4)	95 to 100
2.36-mm (No. 8)	80 to 100
1.18-mm (No. 16)	50 to 85
600-µm (No. 30)	25 to 60
300-µm (No. 50)	5 to 30
150-µm (No. 100)	0 to 10
75-µm (No. 200)	0 to 3.0

 ·        The fine aggregate shall have not more than 45 % passing any sieve and retained on the next consecutive sieve, and its fineness modulus shall be not less than 2.3 nor more than 3.1.

·        Fine aggregate failing to meet these grading requirements then the sample is not according to specifications.

Data sheet

Sieve Number	Sieve Opening (mm)	Materials Retained (gm)	% Materials Retained	Cumulative % Retained	% Passing
3⁄8-in.	9.5
# 4	4.75
#8	2.36
#16	1.18
#30	0.60
#50	0.30
#100	0.15
#200	0.075
Pan	--
Total	Σ=	Σ=

 Calculating % retained =

Percent Passing = (100 – Cumulative percentage retained)

Fineness modulus of fine aggregate =

Gradation chart on a semi log graph paper

 Precautions

 1. Sieves should be cleaned before use.

2. Stiff worn out brushes should not be used.

3. The sieving must be done carefully to prevent the spilling of the aggregate.

4. Do not apply pressure to force the particles through the mesh.

Discussion

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Lab Assignment Questions:

1.     What are fine aggregate, coarse aggregate? Give examples.

2.     What is fineness modulus? What is its significance?

3.     What is the significance of the grading of a mixed or combined aggregate?

4.     What is meant by “good” grading?

5.     What is the practical use of controlling the grading of concrete aggregates?

6.     For the numbered sieves, what does the number indicate?

7.     What is meant by the diameter of opening of a sieve?

8.     Should the sample be weighed to a predetermined weight, if yes Why?

9.     What kind of graph is often drawn, using the test results?

10. How can the coarse and fine aggregates separated out from mixed aggregate?

11. What precautions are taken while performing the experiment?

12. What is the time required to carry out sieving on a sieve shaker?

13. The fineness modulus of sand for concrete should lie within what range of values?

14. What do you understand from the gradation curve?

15. How does the size of aggregate affect the fineness modulus?

16. What is a grading curve and what is its use?